For better or worse, humans have always been de facto commodities. We mouth platitudes about the infinite value of human life, but not a single human behaves as though a human life has more than some finite value in practice.
Elevating humans to very high value benefits us all in some ways, but one must distinguish between that construct and reality as it is a convenient fiction. None of this is without consequences, and the balance has always been toward maximizing the average human value and benefit.
In the end, it is all governed by the dismal science of economics. And no amount of willful ignorance allows one to avoid the economic consequences, good or bad, of the value we put on humans. Stating that "human beings cannot become a legal commodity" is akin to saying "the sun cannot rise in the east". Assertions do not alter the basic properties of the universe, whether we like the consequences of those properties or not.
Where is that written or mandated? Sounds for sure like a commodity right there.